A variety of mechanical systems, such as engines, require means to monitor the quality of oil used for lubrication and other functionalities. A number of prior art methods exist for performing this function, including, for example (1) an odometer monitor to time out the useful life of oil based on general lifetime assumptions, (2) a magnetic field sensor for sensing density of ferromagnetic particles in the oil, (3) a particle separating device to evaluate size and number of contaminating particles, (4) a threshold oil temperature sensor, (5) a corrodable sensor which undergoes electrical circuit break down as oil breaks down or suffers contamination, (6) a chemical prediction device to assess acid content in the oil, and (7) a light absorption sensor based on light attenuation by particles in the oil.
The above described prior art systems suffer from numerous disadvantages, such as, gross insensitivity to critical operating conditions to which oil is subjected, inability to be utilized in many applications due to structural size or geometry limitations, inability to sense other than ferromagnetic debris in the oil, and too specific a measure of oil degradation thereby ignoring many other indicators of oil condition.